The investigators are developing a computer-based neuropsychological assessment tool to help primary care physicians detect neurological and psychiatric disorders. To confirm the tool's efficacy, the investigators will first test the prototype against established tests. The investigators propose to collect preliminary data on a limited group of subjects and age-matched controls. Collecting data on a limited group of subjects provides early insight into how well the tool detects disease, how well patients understand the instructions and enjoy performing the tasks, and if particular trials or stimuli are too difficult or too easy for all subjects. With this information, the investigators can make adjustments to the tool if needed and collect additional data on revised versions of the tool. The data will be used to establish the validity, reliability and sensitivity of the tool to generate consistent and accurate scores. The investigators will initially focus on a limited age range (age fifty-five to seventy-five) and limited set of diseases (early dementias or mild cognitive impairment) to reduce variability within the patient and control groups and to gain more statistical power with a smaller group of subjects.